I have to say that a fight on the sandbarges from the Sarlac Pit scene in "Jedi" would indeed be awesome in MP. You could even have that cannon on the main barge that Leia used.... maybe limit the amount of other areas it could hit so it doesn't completely dominate.

You would be able to jump from skiff to skiff and if you fell off the skiff over the pit you would slide into its belly and it would belch like in the movie. That would be heaven.